Messages in this thread Patch in this message | | | Date | Thu, 26 Jan 2017 23:15:08 +0100 | From | Peter Zijlstra <> | Subject | Re: perf/jit doesn't cope well with mprotect() to jit containing pages |
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On Mon, Dec 12, 2016 at 09:49:03AM +0100, Peter Zijlstra wrote:
> > BTW, it's also a bit weird that those MMAP2 records triggered by > > mprotect/mmap, have prot set to 0... > > Yes, mprotect() does: vma->vm_flags = newflags; before calling > perf_event_mmap(vma); which then looks at VM_{READ,WRITE,EXEC} bits in > that word to generate the prot value. > > So that being 0 is a bit weird.
OK, that was a silly bug :/
With that fixed, the following proglet:
#include <unistd.h> #include <signal.h> #include <stdio.h> #include <malloc.h> #include <stdlib.h> #include <errno.h> #include <sys/mman.h>
void main(void) { void *ptr[5]; int i;
for (i=0; i<5; i++) { ptr[i] = mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); *(char *)ptr[i] = '\0'; mprotect(ptr[i], 4096, PROT_EXEC); } }
Gives:
root@ivb-ep:~# perf record -d ./mprot ... root@ivb-ep:~# perf report -D | grep MMAP2 ... 43805378481 0xc60 [0x60]: PERF_RECORD_MMAP2 2073/2073: [0x7f6ec0862000(0x1000) @ 0x7f6ec0862000 00:00 0 0]: --xp //anon 43805381755 0xcc0 [0x60]: PERF_RECORD_MMAP2 2073/2073: [0x7f6ec0861000(0x1000) @ 0x7f6ec0861000 00:00 0 0]: rw-p //anon 43805392374 0xd20 [0x60]: PERF_RECORD_MMAP2 2073/2073: [0x7f6ec0861000(0x2000) @ 0x7f6ec0861000 00:00 0 0]: --xp //anon 43805395093 0xd80 [0x60]: PERF_RECORD_MMAP2 2073/2073: [0x7f6ec0860000(0x1000) @ 0x7f6ec0860000 00:00 0 0]: rw-p //anon 43805402842 0xde0 [0x60]: PERF_RECORD_MMAP2 2073/2073: [0x7f6ec0860000(0x3000) @ 0x7f6ec0860000 00:00 0 0]: --xp //anon 43805405388 0xe40 [0x60]: PERF_RECORD_MMAP2 2073/2073: [0x7f6ec085f000(0x1000) @ 0x7f6ec085f000 00:00 0 0]: rw-p //anon 43805412605 0xea0 [0x60]: PERF_RECORD_MMAP2 2073/2073: [0x7f6ec085f000(0x4000) @ 0x7f6ec085f000 00:00 0 0]: --xp //anon 43805415134 0xf00 [0x60]: PERF_RECORD_MMAP2 2073/2073: [0x7f6ec085e000(0x1000) @ 0x7f6ec085e000 00:00 0 0]: rw-p //anon 43805422225 0xf60 [0x60]: PERF_RECORD_MMAP2 2073/2073: [0x7f6ec085e000(0x5000) @ 0x7f6ec085e000 00:00 0 0]: --xp //anon
If you omit the mmap_data=1 thing, it looks like:
123087941779 0x500 [0x60]: PERF_RECORD_MMAP2 2084/2084: [0x7fca5a8bd000(0x1000) @ 0x7fca5a8bd000 00:00 0 0]: --xp //anon 123087953825 0x560 [0x60]: PERF_RECORD_MMAP2 2084/2084: [0x7fca5a8bc000(0x2000) @ 0x7fca5a8bc000 00:00 0 0]: --xp //anon 123087962944 0x5c0 [0x60]: PERF_RECORD_MMAP2 2084/2084: [0x7fca5a8bb000(0x3000) @ 0x7fca5a8bb000 00:00 0 0]: --xp //anon 123087971135 0x620 [0x60]: PERF_RECORD_MMAP2 2084/2084: [0x7fca5a8ba000(0x4000) @ 0x7fca5a8ba000 00:00 0 0]: --xp //anon 123087979360 0x680 [0x60]: PERF_RECORD_MMAP2 2084/2084: [0x7fca5a8b9000(0x5000) @ 0x7fca5a8b9000 00:00 0 0]: --xp //anon
--- diff --git a/kernel/events/core.c b/kernel/events/core.c index 896aa53..e67c5ba 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -6660,6 +6683,27 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event) char *buf = NULL; char *name; + if (vma->vm_flags & VM_READ) + prot |= PROT_READ; + if (vma->vm_flags & VM_WRITE) + prot |= PROT_WRITE; + if (vma->vm_flags & VM_EXEC) + prot |= PROT_EXEC; + + if (vma->vm_flags & VM_MAYSHARE) + flags = MAP_SHARED; + else + flags = MAP_PRIVATE; + + if (vma->vm_flags & VM_DENYWRITE) + flags |= MAP_DENYWRITE; + if (vma->vm_flags & VM_MAYEXEC) + flags |= MAP_EXECUTABLE; + if (vma->vm_flags & VM_LOCKED) + flags |= MAP_LOCKED; + if (vma->vm_flags & VM_HUGETLB) + flags |= MAP_HUGETLB; + if (file) { struct inode *inode; dev_t dev; @@ -6686,27 +6730,6 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event) maj = MAJOR(dev); min = MINOR(dev); - if (vma->vm_flags & VM_READ) - prot |= PROT_READ; - if (vma->vm_flags & VM_WRITE) - prot |= PROT_WRITE; - if (vma->vm_flags & VM_EXEC) - prot |= PROT_EXEC; - - if (vma->vm_flags & VM_MAYSHARE) - flags = MAP_SHARED; - else - flags = MAP_PRIVATE; - - if (vma->vm_flags & VM_DENYWRITE) - flags |= MAP_DENYWRITE; - if (vma->vm_flags & VM_MAYEXEC) - flags |= MAP_EXECUTABLE; - if (vma->vm_flags & VM_LOCKED) - flags |= MAP_LOCKED; - if (vma->vm_flags & VM_HUGETLB) - flags |= MAP_HUGETLB; - goto got_name; } else { if (vma->vm_ops && vma->vm_ops->name) {
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